Method of Handling Link Failure and Related Communication Device

ABSTRACT

A communication device for handling a link failure comprises a storage unit for storing instructions and a processing means coupled to the storage unit. The processing means is configured to execute instructions stored in the storage unit. The instructions comprises communicating with a master base station via a first uplink (UL) carrier and a first downlink (DL) carrier; communicating with a secondary base station via a second UL carrier and a second DL carrier; detecting a link failure related to the secondary base station while communicating with the master base station; and transmitting information of the link failure and information of a measurement result related to the secondary base station to the master base station to report the link failure.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/979,016, filed on Apr. 14, 2014 and incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related to a method used in a wirelesscommunication system, and more particularly, to a method of handling alink failure in a wireless communication system.

2. Description of the Prior Art

A long-term evolution (LTE) system supporting the 3rd GenerationPartnership Project (3GPP) Rel-8 standard and/or the 3GPP Rel-9 standardare developed by the 3GPP as a successor of a universal mobiletelecommunications system (UMTS), for further enhancing performance ofthe UMTS to satisfy increasing needs of users. The LTE system includes anew radio interface and a new radio network architecture that provides ahigh data rate, low latency, packet optimization, and improved systemcapacity and coverage. In the LTE system, a radio access network knownas an evolved universal terrestrial radio access network (E-UTRAN)includes multiple evolved Node-Bs (eNBs) for communicating with multipleuser equipments (UEs), and for communicating with a core networkincluding a mobility management entity (MME), a serving gateway, etc.,for Non-Access Stratum (NAS) control.

A LTE-advanced (LTE-A) system, as its name implies, is an evolution ofthe LTE system. The LTE-A system targets faster switching between powerstates, improves performance at the coverage edge of an eNB, andincludes advanced techniques, such as carrier aggregation (CA),coordinated multipoint (CoMP) transmission/reception, uplinkmultiple-input multiple-output (UL-MIMO), etc. For a UE and an eNB tocommunicate with each other in the LTE-A system, the UE and the eNB mustsupport standards developed for the LTE-A system, such as the 3GPPRel-10 standard or later versions.

The UE may receive packets (e.g., transport blocks (TBs)) transmitted bytwo eNBs, when the UE is configured with a dual connectivity. Throughputof the UE is improved when the dual connectivity is operated. However,wireless links between the UE and the eNBs may not be stable due tocharacteristics of the wireless links. For example, a radio link failuremay happen between the UE and one of the eNBs. The UE does not know howto report the radio link failure when the dual connectivity is realizedby the UE and the eNBs. In another example, the UE may fail to completea random access procedure with one of the eNBs. Similarly, the UE doesnot know how to process the failure of the random access procedure. Inanother example, the UE may fail to transmit a radio link control (RLC)packet data unit (PDU) to one of the eNBs, e.g., when the maximum numberof retransmissions is reached. Communications between the UE and theeNBs may not be proceeded regularly, if the retransmission of the RLCPDU cannot be solved.

Thus, how to solve the abovementioned failures of the operations is animportant topic to be discussed.

SUMMARY OF THE INVENTION

The present invention therefore provides a method for handling a linkfailure to solve the abovementioned problem.

A communication device for handling a link failure comprises a storageunit for storing instructions and a processing means coupled to thestorage unit. The processing means is configured to execute instructionsstored in the storage unit. The instructions comprises communicatingwith a master base station via a first uplink (UL) carrier and a firstdownlink (DL) carrier; communicating with a secondary base station via asecond UL carrier and a second DL carrier; detecting a link failurerelated to the secondary base station while communicating with themaster base station; and transmitting information of the link failureand information of a measurement result related to the secondary basestation to the master base station to report the link failure.

A method of handling a link failure for a communication device comprisescommunicating with a master base station via a first uplink (UL) carrierand a first downlink (DL) carrier; communicating with a secondary basestation via a second UL carrier and a second DL carrier; detecting alink failure related to the secondary base station while communicatingwith the master base station; and transmitting information of the linkfailure and information of a measurement result related to the secondarybase station to the master base station to report the link failure.

A communication device for handling a link failure comprises a storageunit for storing instructions and a processing means coupled to thestorage unit. The processing means is configured to execute instructionsstored in the storage unit. The instructions comprises communicatingwith a master base station via a first uplink (UL) carrier and a firstdownlink (DL) carrier; communicating with a secondary base station via asecond UL carrier and a second DL carrier; detecting a link failurerelated to the secondary base station while communicating with themaster base station; and not indicating availability of information ofthe link failure in a message transmitted to the master base station oranother master base station.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a wireless communication systemaccording to an example of the present invention.

FIG. 2 is a schematic diagram of a communication device according to anexample of the present invention.

FIG. 3 is a flowchart of a process according to an example of thepresent invention.

FIG. 4 is a flowchart of a process according to an example of thepresent invention.

DETAILED DESCRIPTION

FIG. 1 is a schematic diagram of a wireless communication system 10according to an example of the present invention. The wirelesscommunication system 10 is briefly composed of a user equipment (UE) 100and base stations (BSs) 102 and 104. In FIG. 1, the UE 100, the BSs 102and 104 and are simply utilized for illustrating the structure of thewireless communication system 10. Practically, the BS 102 and/or the BS104 may be an evolved NB (eNB) and/or a relay station in an evolvedUTRAN (E-UTRAN), a long term evolution (LTE) system, a LTE-Advanced(LTE-A) system or an evolution of the LTE-A system. The wirelesscommunication system 10 may be a time-division duplexing (TDD) system(i.e., the TDD mode is operated) or a frequency-division duplexing (FDD)system (i.e., the FDD mode is operated). In FIG. 1, coverage areas ofthe BS 102 and the BS 104 may be partly overlapped.

As shown in FIG. 1, the UE 100 may be configured to communicate with theBS 102 and the BS 104 at the same time according to a dual connectivityconfigured to the UE 100. That is, the UE 100 may perform atransmission/reception via both the BSs 102 and 104. For example, the UE100 may receive packets (e.g., transport blocks (TBs)) from the BSs 102and 104 according to the dual connectivity, or the UE 100 may transmitpackets (e.g., TBs) to the BSs 102 and 104 according to the dualconnectivity. In general, it means that the UE 100 receives the packetsfrom at least one cell of the BS 102 and at least one cell of the BS 104according to the dual connectivity, when the UE 100 receives the packetsfrom both the BSs 102 and 104. Similarly, it means that the UE 100transmits the packets to at least one cell of the BS 102 and/or at leastone cell of the BS 104 according to the dual connectivity, when the UE100 transmits the packets to both the BSs 102 and 104. In addition, oneof the BSs 102 and 104 may be a master eNB (MeNB) and the other of theBSs 102 and 104 may be a secondary eNB (SeNB) according to the dualconnectivity defined in 3GPP. One of the cell(s) of the MeNBcommunicating with the UE 100 may be a primary cell (PCell) and theother cell(s) (if available) of the MeNB may be secondary cell (s)(SCell(s)). One of the cell(s) of the SeNB communicating with the UE 100may be a primary SCell (PSCell), and the other cell(s) (if available) ofthe SeNB may be SCell(s).

The UE 100 may be a low cost device (e.g., machine type communication(MTC) device), a device-to-device (D2D) device, a mobile phone, alaptop, a tablet computer, an electronic book, a portable computersystem, or combination thereof. In addition, the UE 100, the BS 102 orthe BS 104 may be seen as a transmitter or a receiver according to itstransmission direction, e.g., for an uplink (UL), the UE 100 is thetransmitter and the BS 102 and/or the BS 104 is the receiver, and for adownlink (DL), the BS 102 and/or the BS 104 is the transmitter and theUE 100 is the receiver.

FIG. 2 is a schematic diagram of a communication device 20 according toan example of the present invention. The communication device 20 may bethe UE 100, the BS 102 and/or the BS 104 shown in FIG. 1, but is notlimited herein. The communication device 20 may include a processingmeans 200 such as a microprocessor or Application Specific IntegratedCircuit (ASIC), a storage unit 210 and a communication interfacing unit220. The storage unit 210 may be any data storage device that may storea program code 214, accessed and executed by the processing means 200.Examples of the storage unit 210 include but are not limited to asubscriber identity module (SIM), read-only memory (ROM), flash memory,random-access memory (RAM), Compact Disc Read-Only Memory (CD-ROM),digital versatile disc-ROM (DVD-ROM), Blu-ray Disc-ROM (BD-ROM),magnetic tape, hard disk, optical data storage device, non-volatilestorage unit, non-transitory computer-readable medium (e.g., tangiblemedia), etc. The communication interfacing unit 220 is preferably atransceiver and is used to transmit and receive signals (e.g., data,signals, messages and/or packets) according to processing results of theprocessing means 200.

FIG. 3 is a flowchart of a process 30 according to an example of thepresent invention. The process 30 may be utilized in a communicationdevice (e.g., the UE 100), for handling a link failure. The process 30may be compiled into the program code 214 and includes the followingsteps:

Step 300: Start.

Step 302: Communicate with a master BS via a first UL carrier and afirst DL carrier.

Step 304: Communicate with a secondary BS via a second UL carrier and asecond DL carrier.

Step 306: Detect a link failure related to the secondary BS whilecommunicating with the master BS.

Step 308: Transmit information of the link failure and information of ameasurement result related to the secondary BS to the master BS, toreport the link failure.

Step 310: End.

According to the process 30, the communication device communicates witha master BS (e.g., the BS 102) via a first UL carrier and a first DLcarrier, and communicates with a secondary BS (e.g., the BS 104) via asecond UL carrier and a second DL carrier. The communication device maydetect a link failure (e.g., radio link failure) related to thesecondary BS (e.g., occurred between the communication device and thesecondary BS) while communicating with the master BS. Then, thecommunication device transmits information of the link failure andinformation of a measurement result related to the secondary BS to themaster BS, to report the link failure. That is, the communication deviceprovides the information of the link failure (e.g., for indicating thelink failure) and the information of the measurement result (e.g., forhandling the link failure) to the master BS, to report the link failure.Thus, the master BS can handle the link failure according to theinformation of the measurement result, after receiving the reporting ofthe link failure.

The master BS may handle the link failure in several ways according tothe information of the measurement result to avoid the link failurehappens again. In the first example, the master BS may reconfigure theUE to release the second UL carrier and the second DL carrier if themeasurement result shows that qualities of these carriers are not good.In the second example, the master BS may reconfigure the UE to replacethe second UL carrier and the second DL carrier with a third UL carrierand a third DL carrier respectively if the measurement result shows thatquality of the third DL carrier is good. In the third example, themaster BS may still reconfigure the UE to use the second UL carrier andthe second DL carrier if the measurement result shows that quality ofthe second DL carrier is still good. The master BS may determine that aDL carrier is good if a measurement value of the DL carrier in themeasurement result is greater than a predetermined value.

The first UL carrier and the first DL carrier may be component carriersbelonging to a cell of the master BS. The second UL carrier and thesecond DL carrier may be component carriers belonging to a cell of thesecondary BS. In one example, the master BS may be a master eNB (MeNB),and the secondary BS may be a secondary eNB (SeNB). The cell of the MeNBmay be a PCell and the cell of the SeNB may be a PSCell. There may be aradio resource control (RRC) connection between the communication deviceand the MeNB, and the communication device may be configured tocommunicate with the MeNB and the SeNB, i.e., dual connectivity.

Moreover, the information of the link failure may be included in a firstmessage and the information of the measurement result may be included ina second message. The first message and the second message may be RRCmessages. The communication device may transmit the RRC messages via aRRC connection to the MeNB. Alternatively, the information of the linkfailure and the information of the measurement result may be in a singlemessage. The single message may be a SCGFailurelnfomration message. Thecommunication device may transmit the single message via the RRCconnection to the MeNB. The RRC connection may consist of at least onesignaling radio bearer (SRB) and is established before the link failure.

Realization of the present invention is not limited to the abovedescription.

In one example, the communication device may transmit the first messageincluding the information of the link failure to the master BS, afterdetecting the link failure. Then, the master BS transmits a requestmessage to the communication device in response to the information ofthe link failure. The communication device transmits the information ofthe measurement result to the master BS in response to the requestmessage. The request message may also be a RRC message, e.g.,UEInformationRequest. In short, the communication device transmits thesecond message to the master BS according to the request message. Thatis, the communication device only indicates the link failure to themaster BS at the beginning. The communication device provides theinformation of the measurement result to the master BS, if the requestmessage from the master BS is received. The first message may furtherinclude availability of the information of the measurement result tonotify the master BS or another master BS to retrieve the information ofthe measurement result by using the request message.

The link failure in the process 30 is not limited. There are varioustypes of the link failure. In one example, the link failure may includea radio link failure on the second DL carrier of a cell, e.g., PSCell,due to expiry of a timer of the communication device.

In one example, the communication device may perform a random accessprocedure on the second UL carrier of the cell to the secondary BS whencommunicating with the secondary BS, and the link failure may include arandom access problem related to the random access procedure on thesecond UL carrier. In one example, the link failure may include a radiolink control (RLC) problem where the maximum number of retransmissionson the second UL carrier is reached. The information of the link failuremay indicate a failure type of the link failure as described above. Inother words, the information of the link failure may indicate that theradio link failure on the second DL carrier, the random access problemon the second UL carrier or the RLC problem on the second UL carrierdetected by the communication device. In addition, the information ofthe link failure may or may not further include a Cell Radio NetworkTemporary Identifier (C-RNTI) assigned by the secondary BS.

Detail of the information of the measurement result in the process 30 isnot limited. In one example, the information of the measurement resultmay include measurement value (s) based on measurement (s) on DL signal(s) of the at least one cell of the secondary BS. The measurement value(s) may include at least one of a Reference Signal Received Power (RSRP)and a Reference Signal Received Quality (RSRQ) of at least one cell ofthe secondary BS. Further, if the secondary BS is a SeNB, the at leastone cell may include one or more SCells, wherein one of the SCell (s)may be a PSCell.

Details of the information of the link failure and the information ofthe measurement result in the process 30 are not limited. For example,the information of the measurement result may include at least one ofglobal cell identity, physical cell identity and carrier frequency ofeach of the at least one cell to identify the at least one cell of thesecondary BS to which the measurement result(s) correspond. Theinformation of the measurement result may further include locationinformation of the communication device. For example, the locationinformation may include location coordinates and/or a horizontalvelocity of the communication device.

FIG. 4 is a flowchart of a process 40 according to an example of thepresent invention. The process 40 may be utilized in a communicationdevice (e.g., the UE 100), for handling a link failure. The process 40may be compiled into the program code 214 and includes the followingsteps:

Step 400: Start.

Step 402: Communicate with a master BS via a first UL carrier and afirst DL carrier.

Step 404: Communicate with a secondary BS via a second UL carrier and asecond DL carrier.

Step 406: Detect a link failure related to the secondary BS whilecommunicating with the master BS.

Step 408: Not indicate availability of information of the link failurein a message transmitted to the master BS or another master BS.

Step 410: End.

According to the process 40, the communication device communicates witha master BS (e.g., the BS 102) via a first UL carrier and a first DLcarrier, and communicates with a secondary BS (e.g., the BS 104) via asecond UL carrier and a second DL carrier. The communication device maydetect a link failure (e.g., radio link failure) related to thesecondary BS, e.g., occurred between the communication device and thesecondary BS, while communicating with the master BS. Then, thecommunication device does not indicate availability of information ofthe link failure in a message transmitted to the master BS or anothermaster BS. That is, the communication device does not notify theavailability of the link failure related to the secondary BS to themaster BS or another master BS. Thus, the master BS or the other masterBS does not transmit a request message for requesting the communicationdevice to transmit a response message including the information of thelink failure. The problem that the master BS or the other BS may obtainthe information of the link failure incorrectly is avoided, because thecommunication device does not notify the availability of the informationof the link failure related to the secondary BS. Moreover, anotherproblem is that it will be a duplicate reporting of the information ofthe link failure if the communication device transmits the informationof the link failure according to process 30, and the communicationdevice transmits the information of the link failure to the master BSagain due to that the master BS transmits the request message inresponse to the availability of the information of the link failure. Theother problem is also avoided.

In one example, the availability of the information of the link failuremay include rlf-Info-Available, and the message may be aRRCConnectionReconfigurationComplete message, aRRCConnectionReestablishmentComplete message or aRRCConnectionSetupComplete message. The master BS may be a MeNB and thesecondary BS may be a SeNB. The first UL carrier and the first DLcarrier may be component carriers of a PCell of the MeNB. The second ULcarrier and the second DL carrier may be component carriers of a PSCellof the SeNB. The request message may be a UEInformationRequest message,and the response message may be a UEInformationResponse message. Thatis, the communication device does not include the rlf-Info-Available inthe RRCConnectionReconfigurationComplete message and/or theRRCConnectionSetupComplete message transmitted to the MeNB, when thelink failure is related to the SeNB. Thus, the MeNB or the other MeNBdoes not transmit the UEInformationRequest message to the communicationdevice.

Realization of the present invention is not limited to the abovedescription.

The link failure in the process 40 is not limited. There are varioustypes of the link failure. In one example, the link failure may includea radio link failure on the second DL carrier of a cell, e.g., PSCell,due to expiry of a timer of the communication device. In one example,the communication device may perform a random access procedure on thesecond UL carrier of the cell to the secondary BS when communicatingwith the secondary BS, and the link failure may include a random accessproblem related to the random access procedure on the second UL carrier.In one example, the link failure may include a RLC problem where themaximum number of retransmissions on the second UL carrier is reached.The information of the link failure may indicate a failure type of thelink failure as described above. In other words, the information of thelink failure may indicate that the radio link failure on the second DLcarrier, the random access problem on the second UL carrier or the RLCproblem on the second UL carrier detected by the communication device.In addition, the information of the link failure may or may not furtherinclude a C-RNTI assigned by the secondary BS.

Detail of the information of the link failure which is not transmittedin the process 40 is not limited. In one example, the information of thelink failure may relate to at least one cell of the secondary BS. Forexample, if the secondary BS is a SeNB, the at least one cell mayinclude one or more SCells, wherein one of the SCell(s) may be a PSCell.The information of the link failure may include at least one of a globalcell identity, a physical cell identity and a carrier frequency of eachof the at least one cell.

Furthermore, the communication device may detect another link failurerelated to the master BS (e.g., occurred between the communicationdevice and the master BS), and indicate availability of information ofthe other link failure to the master BS or another master BS. That is,the communication device notifies availability of the information of thelink failure related to the master BS to the master BS or the othermaster BS, but does not notify availability of a link failure related tothe secondary BS to the master BS or the other master BS. For example,while communicating with a SeNB, the communication device may detect aradio link failure on the first DL carrier of a cell of a MeNB, a randomaccess problem when performing a random access procedure on the first ULcarrier of the cell of the MeNB to the MeNB or a RLC problem whentransmitting a RLC PDU on the first UL carrier of the cell of the MeNBto the MeNB. The communication device may perform a RRC connectionreestablishment procedure by transmitting aRRCConnectionReestabishmentRequest message to the MeNB or another MeNB.The communication device may include rlf-Info-Available in aRRCConnectionReestablishmentComplete message of the RRC connectionreestablishment procedure. Moreover, after performing the RRC connectionreestablishment procedure, the communication device may include therlf-Info-Available in a RRCConnectionReconfigurationComplete messageresponding to a RRCConnectionReconfiguration message received from theMeNB or another MeNB, if the communication device has not transmittedthe information of the link failure to the MeNB or the other MeNB. Afterperforming the RRC connection reestablishment procedure, thecommunication device may include the rlf-Info-Available in aRRCConnectionSetupComplete message responding to a RRCConnectionSetupmessage received from the MeNB or another MeNB, if the communicationdevice has not transmitted the information of the link failure to theMeNB or the other MeNB.

A carrier (UL carrier or DL carrier) mentioned above may be a FDDcarrier for the FDD mode or a TDD carrier for the TDD mode. The FDDcarrier may include subframes with the same transmission direction(e.g., UL or DL). The TDD carrier may include subframes with differenttransmission directions, and the transmission directions of thesubframes are determined according to a UL/DL configuration of the TDDcarrier.

Those skilled in the art should readily make combinations, modificationsand/or alterations on the abovementioned description and examples. Theabovementioned steps of the processes including suggested steps can berealized by means that could be a hardware, a firmware known as acombination of a hardware device and computer instructions and data thatreside as read-only software on the hardware device, or an electronicsystem. Examples of hardware can include analog, digital and mixedcircuits known as microcircuit, microchip, or silicon chip. Examples ofthe electronic system can include a system on chip (SOC), system inpackage (SIP), a computer on module (COM), and the communication device20. Process 30 and process 40 may be combined together to solve theproblems as described above.

To sum up, the present invention provides a method of handling a linkfailure. The communication device transmits information of the linkfailure to a BS according to the present invention, such that the BS canhandle the link failure properly and incorrect processing of theinformation is avoided. Thus, the operation of the communication deviceand the BS is performed regularly.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A communication device for handling a linkfailure, comprising: a storage unit for storing instructions of:communicating with a master base station via a first uplink (UL) carrierand a first downlink (DL) carrier; communicating with a secondary basestation via a second UL carrier and a second DL carrier; detecting alink failure related to the secondary base station while communicatingwith the master base station; and transmitting information of the linkfailure and information of a measurement result related to the secondarybase station to the master base station to report the link failure; anda processing means, coupled to the storage unit, configured to executethe instructions stored in the storage unit.
 2. The communication deviceof claim 1, wherein the information of the link failure and theinformation of the measurement result are in a single message.
 3. Thecommunication device of claim 1, wherein the information of the linkfailure indicates a radio link problem on the second DL carrier, arandom access problem on the second UL carrier or a radio link control(RLC) problem on the second UL carrier detected by the communicationdevice.
 4. The communication device of claim 1, wherein the informationof the measurement result comprises at least one of a Reference SignalReceived Power (RSRP) and a Reference Signal Received Quality (RSRQ)related to the secondary base station.
 5. The communication device ofclaim 1, wherein the information of the measurement result is related toat least one cell of the secondary base station.
 6. The communicationdevice of claim 5, wherein the information of the measurement resultfurther comprises at least one of at least one global cell identity, atleast one physical cell identity and at least one carrier frequency ofthe at least one cell.
 7. A method of handling a link failure for acommunication device, the method comprising: communicating with a masterbase station via a first uplink (UL) carrier and a first downlink (DL)carrier; communicating with a secondary base station via a second ULcarrier and a second DL carrier; detecting a link failure related to thesecondary base station while communicating with the master base station;and transmitting information of the link failure and information of ameasurement result related to the secondary base station to the masterbase station to report the link failure.
 8. The method of claim 7,wherein the information of the link failure and the information of themeasurement result are in a single message.
 9. The method of claim 7,wherein the information of the link failure indicates a radio linkproblem on the second DL carrier, a random access problem on the secondcarrier or a radio link control (RLC) problem on the second UL carrierdetected by the communication device.
 10. The method of claim 7, whereinthe information of the measurement result comprises at least one of aReference Signal Received Power (RSRP) and a Reference Signal ReceivedQuality (RSRQ) related to the secondary base station.
 11. The method ofclaim 7, wherein the information of the measurement result is related toat least one cell of the secondary base station.
 12. The method of claim11, wherein the information of the measurement result further comprisesat least one of at least one global cell identity, at least one physicalcell identity and at least one carrier frequency of the at least onecell.
 13. A communication device for handling a link failure,comprising: a storage unit for storing instructions of: communicatingwith a master base station via a first uplink (UL) carrier and a firstdownlink (DL) carrier; communicating with a secondary base station via asecond UL carrier and a second DL carrier; detecting a link failurerelated to the secondary base station while communicating with themaster base station; and not indicating availability of information ofthe link failure in a message transmitted to the master base station oranother master base station; and a processing means, coupled to thestorage unit, configured to execute the instructions stored in thestorage unit.
 14. The communication device of claim 13, wherein theavailability of the information of the link failure comprisesrlf-Info-Available.
 15. The communication device of claim 13, whereinthe information of the link failure indicates a radio link problem onthe second DL carrier, a random access problem on the second UL carrieror a radio link control (RLC) problem on the second UL carrier detectedby the communication device.
 16. The communication device of claim 13,wherein the information of the link failure is related to at least onecell of the secondary base station.
 17. The communication device ofclaim 16, wherein the information of the link failure comprises at leastone of at least one global cell identity, at least one physical cellidentity and at least one carrier frequency of the at least one cell.18. The communication device of claim 13, wherein the instructionsfurther comprise: detecting another link failure related to the masterbase station; and indicating availability of information of the otherlink failure to the master base station or the other master basestation.